Missing Issues Mid-run of Popular Characters (Rant/Venting)?

I did a search and see that there are a lot of questions regarding missing issues. But I didn’t see an real answers to missing issues in the middle of a run.

Example: I’ve been working my way through ASM vol 1 and now that title is making references to Peter Parker: The Spectacular Spider-Man. So, I hopped over to that comic to see that issues 71-80, 84, 87-89 are missing. ASM keeps referring to a war between Doc Ock and the Owl with Black Cat in the middle (last I had heard of her Spidey thought she had drowned). But I can’t read that story line because it doesn’t seem to be in MU.

Just seems odd to have missing issues of a Spider-Man title like that in the middle of the run. I’d understand if they had 1-100, but had not scanned the rest, or it was a less popular character. Just seems weird for Spider-Man.